High temperature alloy



United; States Patent HIGH TEMPERATURE ALLOY Marion Semchyshen,Deal-born, Mich., assignor to American Metal Climax, Inc., 'New York,N.Y., a corporation of New York No Drawing. Filed Sept. 10, 1958, Ser.No. 760,065

3 Claims. (Cl. 75-176) The present invention relates to castmolybdenum-base alloys. The object of the invention is to provide amolybdenum-base alloy casting capable of being worked at elevatedtemperatures and having high strength at temperatures above 1600 F.

As set forth in United States Patent 2,678,269, it has been known thathighly advantageous properties are obtained with molybdenum castingscontaining from .25% to 14% titanium and from 01% to .25 carbon.However, it has previously been thought that quantities of carbon inexcess of .07% increase the difficulty of working the alloy withoutproducing any compensated advantage. In accordance with the presentinvention, it is now found that if the titanium content ofmolybdenumbase castings is increased above the lower portion of therange set forth in United States Patent 2,678,269, decided advantagesflow from the employment of a carbon content in the range of .30% to .75

The alloys of the present invention contain from 1.00% to 8.00% titaniumand from 30% to .75 carbon. Such alloys in the form of castings may beworked at elevated temperatures in the range of 2300 F. to 3000" F.,provided the oxygen content does not exceed .005%. The preferred alloyscontain less than .002% oxygen.

The benefits of the present invention are also realized if smallquantities of zirconium are present. Accordingly, it may be included asan optional constituent in amounts up to but not more than about .50%.In addition a portion of the molybdenum may be replaced by tungsten upto a maximum tungsten content equalling the molybdenum content. In allcases the balance of the alloy is molybdenum or molybdenum and tungsten.

The alloy of the present invention may be prepared by arc-melting invacuum, preferably using a furnace of the type disclosed in UnitedStates Patent 2,656,743. Carbon is added to react with any oxygenpresent in raw materials and in a quantity which will leave the desiredexcess in the final casting. The best results are obtained when theresidual carbon content increases proportionately within the abovestated range as the titanium content increases within the range stated.The absolute ice pressure during the melting operation is preferablymaintained below microns of mercury.

The raw material used in making the new alloy consists of molybdenumpowder having an oxygen content ranging from .012% to 029% and titaniumsponge having an oxygen content below .20%.

A specific example of a new alloy in accordance with the presentinvention is an alloy containing .50% carbon, 3.20% titanium and notmore than .002% oxygen. This alloy is found to have a tensile strengthin a fully recrystallized condition at a temperature of 1800 F. of51,000 pounds per square inch, which makes the alloy one of thestro'ngest known materials at that temperature in a fully recrystallizedcondition. Other examples of the invention include an alloy containing38% carbon and 1.17% titanium, an alloy containing .75% carbon and 4.63%titanium, and an alloy containing .75% carbon and 8.00% titanium. Eachof the above mentioned examples contain molybdenum as the balance of thecomposition.

An example of an alloy which also includes zirconium is one containing1.27% titanium, .29% zirconium, and 30% carbon, the balance consistingessentially of molybdenum.

In any of the foregoing examples a portion of the molybdenum may bereplaced by tungsten so long as the tungsten content does not exceed themolybdenum content.

All proportions given are proportions by weight.

What is claimed is:

-1. A cast molybdenum-base alloy capable of being worked at elevatedtemperatures and containing from 30% to .75% carbon, from 1.00% to 8.00%titanium, not more than .005 oxygen, and the balance consistingessentially of molybdenum.

2. A cast molybdenum-base alloy capable of being worked at elevatedtemperatures and containing .50% carbon, 3.20% titanium, and the balanceconsisting essentially of molybdenum.

3. A cast molybdenum-base alloy capable of being worked at elevatedtemperatures and containing from 30% to .75% carbon, from 1.00% to 8.00%titanium, not more than .005 oxygen, not more than about 50% zirconium,and the balance consisting essentially of metal from the groupconsisting of molybdenum and tungsten with the molybdenum content beingat least equal to the tungsten content.

References Cited in the file of this patent UNITED STATES PATENTS Ham etal May 11, 1954 Blank et a1 Feb. 5, 1957 OTHER REFERENCES

1. A CAST MOLYBDENUM-BASE ALLOY CAPABLE OF BEING WORKED AT ELEVATEDTEMPERATURES AND CONTAINING FROM .30% TO .75% CARBON, FROM 1.00% TO8.00% TITANIUM, NOT MORE THAN .005% OXYGEN, AND THE BALANCE CONSISTINGESSENTIALLY OF MOLYBDENUM.